1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a mobile liquid crystal display device that reduces power consumption and a driving method thereof.
2. Discussion of the Related Art
A liquid crystal display device controls the light transmittance of a liquid crystal having dielectric anisotropy by use of an electric field to display a picture. To this end, the liquid crystal display device includes a liquid crystal display panel having a pixel matrix and a drive circuit for driving the liquid crystal display panel. Specifically, the liquid crystal display device, as shown in FIG. 1, includes a liquid crystal display panel 10 having a pixel matrix, a gate driver 12 for driving the gate lines GL of the liquid crystal display panel 10, a data driver 14 for driving the data lines DL of the liquid crystal display panel 10, and a timing controller 16 for controlling the gate driver 12 and the data driver 14.
The liquid crystal display panel 10 includes a pixel matrix composed of pixels formed at each intersection of the gate lines GL and the data lines DL. Each pixel includes a liquid crystal cell Clc which controls the light transmittance in accordance with a data signal, and a thin film transistor TFT for driving the liquid crystal cell Clc. The thin film transistor TFT receives and maintains a data signal from the data line DL in the liquid crystal cell Clc in response to a scan signal of the gate line GL. The liquid crystal Clc changes the arrangement state of the liquid crystal in accordance with the data signal to control the light transmittance, thereby realizing a gray level.
The gate driver 12 sequentially supplies the scan signal to the gate lines GL in response to the control signal from the timing controller 16. The data driver 14 converts a digital data signal from the timing controller 16 into an analog data signal to supply to the data lines DL. The timing controller 16 supplies a control signal to control the gate driver 12 and the data driver 14 and supplies the digital data to the data driver 14.
Small liquid crystal display devices with the above-described features are mainly used in mobile applications. However, power consumption must be reduced for such applications. To this end, a mobile liquid crystal display device, as shown in FIG. 2, uses a line inversion method that inverts the polarity of the liquid crystal cell for each horizontal line.
As shown in FIG. 3, the line inversion method inverts the polarity of the common voltage Vcom for each horizontal synchronization period 1H when the gate line is driven by the gate signal Vgate, thereby enabling to reduce the data voltage Vdata. However, even using the line inversion method, the power consumption is rather high due to the frequency of the common voltage Vcom. Thus, a method which can reduce the power consumption is needed.